1. Field of the Invention
The present invention relates to a tape tension control apparatus for a video cassette recorder (VCR), and more particularly to a tape tension control apparatus capable of precisely controlling the tension of a tape in accordance with the using purpose by use of photosensors and a Hall sensor.
2. Description of the Prior Art
Recently, VCRs have been rapidly popularized with the progress of magnetic recording technologies. With the spread of VCRs, there have been a demand for VCRs being inexpensive, but having a variety of functions.
Refering to FIG. 1, there is illustrated a conventional VCR having a tape tension control function.
In FIG. 1, the reference numeral 12 denotes a rotatable head drum 12 slantly arranged at predetermined angle on a chassis (not shown) supporting a tape cassette 18. The head drum 12 faces the front surface of the tape cassette 18. The tape cassette 18 of the general type has a supply reel 7, a take-up reel 8, and a tape 9 wound around the supply reel 7 and the take-up reel 8. The tape 9 from the supply reel 7 is taken out of the tape cassette 18 via guide posts a and b, wound around the head drum 12 via a tension post 1, an impedance roller 17a and guide posts 10 and 11, introduced in the tape cassette 18 again via guide posts 13 and 14, a capstan 15, a pinch roller 17 and a guide roller 16, and then taken up around the take-up reel 8 via guide posts a and b.
The conventional VCR having the above-mentioned construction includes a tension control device. As shown in FIG. 1, the conventional tension control device comprises a tension lever 2 pivotally mounted to the chassis and attached at one end thereof with the tension post 1, and a tension spring 3 connected at one end thereof to the other end of the tension lever 2 and at the other end thereof to the chassis. A tension band 5 is wound around a part of a peripheral surface of the supply reel 7 so as to adjust the tension of the tape 9. The tension band 5 has one end connected to a fixing member 6 fixedly mounted to the chassis and tile other end connected to a connecting member 4 pivotally mounted to the tension lever 2.
Now, an operation of the conventional tape tension control device having the above-mentioned construction will be described.
In a play mode operation of The VCR, The Tape 9 from the supply reel 7 is taken out of the tape cassette 18 and then wound around a part of the peripheral surface of the tension post 1. Thereafter, the tape 9 comes into contact with the peripheral surface of the rotating head drum 12. Under the condition, the tape 9 is travelled by a frictional feeding force applied thereto by the capstan 15 and the pinch roller 17. When a tension of the tape 9 is excessively increased during the travel of the tape 9, the tension lever 2 pivots about a pin 19 in clockwise by the tension applied thereto via the tension post 1. As a result, the tension of the tension band 5 applied as a frictional force to the supply reel 7 is decreased, thereby causing the amount of the tape 7 being taken out to be increased. Accordingly, the tension of the tape 9 is controlled to be decreased. On the contrary, when the tension of the tape 9 is excessively decreased during the travel of the tape 9, the tension lever 2 pivots about the pin 19 in anti-clockwise by the resilience of the tension spring 3. As a result, the frictional force of the tension band 5 applied to the supply reel 7 is increased, thereby causing the amount of the tape 7 being taken out to be decreased. Accordingly, the tension of the tape 9 is controlled to be increased.
However, it is difficult to constantly maintain the tension of the tape 9. This is because the above-mentioned tension control operations are continuously repeated during the travel of the tape. Furthermore, the conventional tape tension control device has a limitation on a precise control because the tension of the tape is controlled by the tension spring, the tension band, and the connecting member connecting the tension lever and the tension band.
Recently, more various and precise tension controls have been required with a variety of functions of VCRs and various kinds of tapes including a ferrite tape and a metal tape which are used in high density (HD) VORs recently developed. However, known tension control devices could not satisfy such a requirement.